When aircraft are being loaded or unloaded it is common to use boarding bridges that lead directly from the aircraft into the terminal building. However, airports increasingly have large numbers of docking locations that are not sufficiently close to the terminal building for these boarding bridges to be used. Further, even when the docking location is close to the terminal building, a direct boarding bridge is not always available.
It is known to use mobile staircases that can be wheeled to the location of the aircraft on the tarmac. These have the advantage of being useable wherever the aircraft docks. These mobile staircases are often used in combination with buses, such that the buses transport the passengers over the distance between the aircraft and the terminal building and the passengers each individually climb the mobile staircase.
For passengers who are less mobile or disabled, these mobile staircases do not provide a useable route for embarking or disembarking the aircraft. Manually lifting and carrying such passengers is sometimes carried out but this is not a desirable solution and presents health and safety issues.
The usual solution to this problem is the provision of a mobile lifting unit that can be brought to the aircraft on request. Such mobile lifting units are able to lift a passenger, such as a passenger in a wheelchair, between ground level and the aircraft door level.
Similar issues may be encountered with respect to loading and unloading passengers from other craft, such as ships (especially cruise liners). Generally, any craft that are loaded and unloaded with passengers via an entrance/exit that is raised above ground level can encounter these types of problem.